Diplomats and experts are the first to admit that the digital blitz being waged on Twitter, Facebook and YouTube will never be a panacea to combat the jihadists.

But US officials see social media as an increasingly crucial battlefield as they aim to turn young minds in the Muslim world against groups like IS and Al-Qaeda.

For the past 18 months, US officials have targeted dozens of social network accounts linked to Islamic radicals, posting comments, photos and videos and often engaging in tit-for-tat exchanges with those which challenge America.

At the US State Department, employees at the Center for Strategic Counterterrorism Communications (CSCC), created in 2011, manage an Arabic-language Twitter account set up in 2012, an English-language equivalent and a Facebook page, launched this week.

'Many skirmishes, few battles'

A senior US State Department official described the strategy as a kind of cyber guerrilla campaign.

"It is not a panacea, it is not a silver bullet," the official explained. "People exaggerate, people think this is worthless or they think it a magic thing that will make the extremists surrender. It is neither one of those. It is slow, steady, daily engagement pushing back on a daily basis.

"It is a war of thousands of skirmishes, but no big battles. America likes big battles but it is not -- it is like guerrilla warfare," said the official.

The murder of US journalist James Foley, whose execution by Islamic State militants on August 19 was released in a video on the Internet, jolted the new breed of US cyber-warriors into a frenzy.

Since Foley's murder, the CSCC has ramped up its Twitter campaign, posting tributes to the slain reporter, opinion pieces and analyses on radical Islam from across the international media, along with cartoons and graphic photos.

The State Department last week tweeted about the death in Syria of Islamic State members, one of whom, Abu Moussa, had recently declared that the group would one day "raise the flag of Allah in the White House."

Another tweet congratulated militant Yazidis who claimed to have killed 22 Islamic State fighters in Iraq.

Another post was more in keeping with the sober diplomatic tone Washington is used to, a photo-montage showing Syria's leader Bashar Al-Assad alongside Islamic State leader Abu Bakr al-Baghdadi in front of a city in ruins.

"Baghdadi and Assad in a race to destroy Syria - don't make it worse," reads a message.

Historic parallels

The US-managed Twitter accounts are also not squeamish about reproducing images distributed by jihadists depicting mass executions, drawing historic parallels between Islamic State militants and the Nazis.

One post showed armed Islamic State fighters standing over a ditch filled with executed people, alongside another almost identical image of Nazis killing people in similar circumstances.

Satire is also used to undermine militants, with one re-tweeted cartoon referring to the "ISIS bucket challenge" featuring a participant named as "the civilized world" being drenched by a bucket of blood.

The US officials say the social media offensive is an attempt to "contest space" on social networks which had previously been dominated by Islamist radicals.

"This is an area, a field, where before we came along the adversaries had this space to themselves," the official explained.

"You had English language extremists that could say any kind of poison and there will be very low push-back against them," he added. The ultimate aim is to make youths in the West or Muslim nations think twice before embarking on a journey to Syria or Iraq to join Islamic State fighters.

US officials are also mindful of striking the right tone as they troll Islamists.

"Twitter is unfortunately or fortunately a platform which is suitable for what we call snark, sarcasm, for insulting people," the official said. "This is something also we are trying to do, we try to attack.

"We are respectful about things, the loss of human life of innocent people, victims of AQ or victims of ISIS, that is not something for sarcasm.

"But when you are mocking them, it is effective to draw the comparison between what they say and what they do. The hypocrisy of this group is a weakness."

William Braniff, executive director of National Consortium for the Study of Terrorism and Responses to Terrorism (START) at the University of Maryland, said the US online strategy was a step in the right direction but would take a while to yield results.

"For a decade the government is criticized for not engaging in the world of ideas online," Braniff said.

"The department of State eventually created this program in part to address that criticism.

"This is a just a drop in a bucket -- there is so much extremist propaganda online and so many formats for extremists to dialogue that this is really just spitting into the wind.